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Manyurbanareasallovertheworldareaffectedbyawidespectrumofdangersrelatedtoeithernaturalphenomena or human activities. Among natural phenomena, slow-moving landslides are widespread and their interaction with the urban environment often originate detrimental effects to existing facilities (e.g., buildings and infrastructures) withrelatedsocialconsequencesandeconomiclosses.Forthesereasons,landslidehazardandvulnerabilityanalysesrepresentkeystepsforareliablepredictionoftheexpecteddamagetoexposedfacilitiesaswellasforproperly designing and implementing the most suitable risk mitigation strategies. Synthetic Aperture Radar (SAR) data processed via advanced interferometric techniques (DInSAR), such as the onebasedontheuseofSARTomography,canbeextremelyusefulinprovidinglong-termground/facilitydisplacementarchives.Inthisregard,theavailabilityofrecenthigh-resolutionX-BandSARdatapromotedthemonitoring capabilities in urban environments, leading to a major step toward the risk analysis at single facility level. In this study, with reference to an urban area located in Calabria region (southern Italian Apennines) - were the existence of several slow-moving landslides of different types interacting with masonry and reinforced concrete buildings can be recognized - the DInSAR-derived differential settlements experienced by a given building are combined with the corresponding damage severity level (recorded via in-situ surveys) to retrieve the relationship between cause (differential settlements) and effect (damage) for both masonry and reinforced concrete buildings. The obtained results represent the knowledge basis to generate more sophisticated tools (e.g. fragility and vulnerability curves) useful for risk analysis purposes.

In the framework of MORFEO project, financed by the Italian Space Agency (ASI), a study is currently under way to estimate and validate monitoring technologies of deformations with SAR data, to the implementation of a pre-operational service supporting the Civil Protection Department in landslide risk monitoring. The study on ground deformations is performed in MORFEO by applying two different technologies: SBAS developed by CNR-IREA in Naples and SPINUA developed by Politecnico of Bari. These technologies work with SAR data in C band and the use of X band data acquired by COSMO/SKY-MED is under trial. In particular the present report describes the generation and validation activities of EO SAR products (Synthetic Aperture Radar) obtained in landslide areas in Lombardia and Umbria by using ascending and descending passages of ENVISAT satellite. The results obtained in Umbria highlight the presence of deformation phenomena in the area corresponding to the landslide region in Ivancich (Assisi). A general accordance between GPS and SAR sets results by the comparison. In Lombardia GPS deformation time sets have been estimated for SAR data validation. This has highlighted the potential and limits of SAR interferometric techniques for landslide monitoring in an alpine context. Moreover, a first multi-temporal interferometric analysis in X band has been carried out through the SPINUA algorithm. Preliminary results over the area of GARZENO (COMO) show that even with a limited number of COSMO/SkyMED images, there is a good agreement with linear displacement rate maps estimated in C-band. An accurate investigation shall be feasible as soon as a consistent number of COSMO/SkyMED acquisitions is available (not less than 25-30).

The paper deals with the use of multipass synthetic aperture radar (SAR) data in order to achieve three-dimensional tomography reconstruction in presence of volumetric scattering. Starting from azimuth- and range-focused SAR data relative to the same area, neglecting any mutual interaction between the targets, and assuming the propagation in homogeneous media, we investigate the possibility to focus the data also in the elevation direction. The problem is formulated in the framework of linear inverse problem and the solution makes use of the singular value decomposition of the relevant operator. This allows us to properly take into account nonuniform orbit separation and to exploit a priori knowledge regarding the size of the volume interested by the scattering mechanism, thus leading to superresolution in the elevation direction. Results obtained on simulated data demonstrate the feasibility of the proposed processing technique.

We present a new differential synthetic aperture radar (SAR) interferometry algorithm for monitoring the temporal evolution of surface deformations. The presented technique is based on an appropriate combination of differential interferograms produced by data pairs characterized by a small orbital separation (baseline) in order to limit the spatial decorrelation phenomena. The application of the singular value decomposition method allows us to easily "link" independent SAR acquisition datasets, separated by large baselines, thus increasing the observation temporal sampling rate. The availability of both spatial and temporal information in the processed data is used to identify and filter out atmospheric phase artifacts. We present results obtained on the data acquired from 1992 to 2000 by the European Remote Sensing satellites and relative to the Campi Flegrei caldera and to the city of Naples, Italy, that demonstrate the capability of the proposed approach to follow the dynamics of the detected deformations.

The authors present a new spotlight SAR data-focusing algorithm based on a two-step processing strategy that combines the advantages of two commonly adopted processing approaches: the efficiency of SPECAN algorithms and the precision of stripmap focusing techniques. The first step implements a linear and space-invariant azimuth filtering that is carried out via a deramping-based technique representing a simplified version of the SPECAN approach. This operation allows performing a bulk azimuth raw data compression and achieving a pixel spacing smaller than (or equal to) the expected azimuth resolution of the fully focused image. Thus, the azimuth spectral folding phenomenon, typically affecting the spotlight data, is overcome, and the space-variant characteristics of the stripmap system transfer function are preserved. Accordingly, the residual and precise focusing of the SAR data is achieved by applying a conventional stripmap processing procedure requiring a minor modification and implemented in the frequency domain. The extension of the proposed technique to the case of high bandwidth transmitted chirp signals is also discussed. Experiments carried out on real and simulated data confirm the validity of the presented approach, which is mainly focused on spaceborne systems

We investigate the possibility to generate a large-scale Digital Elevation Model by applying the Synthetic Aperture Radar interferometry technique and using tandem data, acquired by the ERS-1/ERS-2 sensors. The presented study is mainly focused on the phase unwrapping step that represents the most critical point of the overall processing chain. In particular, rye concentrate on the unwrapping problems related to the use of a large ERS tandem data set that, in order to be unwrapped, must be partitioned. The paper discusses the inclusion of external information (even rough) of the scene topography, the application of a region growing unwrapping technique and the insertion of possible constraints on the phase to be retrieved in order to minimize the global unwrapping errors. Our goal is the generation of a digital elevation model relative to an area of 300 km by 100 km located in the southern part of Italy. Comparisons between the achieved result and a precise digital terrain model, relative to a smaller area, are also included.

Volcanoes deform dynamically due to changes in both their magmatic system and instability of their edifice. Mt. Etna features vigorous and almost continuous eruptive activity from its summit craters and periodic flank eruptions. Even though its shape is that of a large stratovolcano, its structure features two rift systems and a flank collapse structure similar to Hawaiian shield volcanoes. We analyze European remote sensing (ERS) satellite differential interferometric synthetic aperture radar (InSAR) data (1993–1996) for Mt. Etna spanning its quiescence from 1993 through the initiation of renewed eruptive activity in late 1995. We use synthetic aperture radar (SAR) data from both ascending and descending ERS satellite tracks. Comparison of independent interferograms covering the first 2 years of the inflationary period shows a pattern consistent with inflation of the volcano. Calculation of the tropospheric path delay based on meteorological data does not change this interpretation. Interferograms from late summer 1995–1996 show no significant deformation. Joint inversion of interferograms from ascending and descending satellite tracks require both inflation from a spheroidal magmatic source located beneath the summit at 5 km below sea level, and displacement of the east flank of Etna along a basal decollement. Both sources of deformation were contemporaneous within the resolution of our data and suggest that inflation of the central magma chamber acted to trigger slip of Etna's eastern flank. These results demonstrate that flank instability and recharge of a volcano's magma system must both be considered toward understanding how volcanoes work and in their hazard evaluation.